When do girls have periods?

The age range for when girls first get their periods, also called menarche, can vary widely. It typically occurs between the ages of 12 and 15, although it can begin as early as 9 or as late as 16 or even older. The average age for menarche in the United States is around 12.4 years. There are a number of factors that can affect the age of menarche, including genetics, ethnicity, and overall health.